Bisilane synergistically modified nano calcium carbonate superhydrophobic coating, concentrate and preparation method thereof

Abstract

The application discloses a kind of double silane synergic modification nano calcium carbonate super-hydrophobic coating, concentrated solution and preparation method thereof, belong to hydrophobic coating material technical field.The preparation method of concentrated solution includes: after stirring uniformly with isopropyl alcohol, deionized water and formic acid, adding dodecyl trimethoxysilane and 3-(isobutenoyloxy) propyl trimethoxysilane, stirring uniformly and standing, to obtain mixed silanol solution;Nano calcium carbonate and nano zinc oxide are added, and the mixed system is prepared by ultrasonic treatment;Filtering is obtained after heating and stirring reaction, cooling down.The concentrated solution is sprayed to the surface of concrete test to prepare super-hydrophobic coating.The application is crosslinked with double silane synergic, and micro-nano double rough structure is constructed by collocating nanoparticles, which can realize the modification of concrete surface super-hydrophobic film forming and superficial layer pore wall hydrophobic modification simultaneously, and has low surface energy hydrophobic characteristics and high interface combination stability.

Description

Technical Field

[0001] This invention relates to the field of surface protection technology for building materials, specifically to a dual-silane synergistic modified nano-calcium carbonate superhydrophobic coating, a concentrated solution, and a preparation method thereof. More specifically, it relates to a highly weather-resistant dual-silane synergistic modified nano-calcium carbonate concrete hydrophobic coating, a concentrated solution, and a preparation method thereof. This coating is suitable for extreme climatic environments such as the Qinghai-Tibet Plateau, characterized by strong ultraviolet radiation, large diurnal temperature variations, frequent freeze-thaw cycles, and significant wind and sand erosion. It can provide long-term protection for concrete with strength grades of C40 and above, belonging to the interdisciplinary technical field of cementitious material surface modification and extreme environment protection materials. Background Technology

[0002] The unique geographical location and extreme climate of the Qinghai-Tibet Plateau provide a typical extreme service environment for concrete structures: strong solar ultraviolet radiation, huge diurnal temperature variations, frequent freeze-thaw cycles, wind and sand erosion, and hail impacts combine to easily lead to the deterioration of surface microstructure and performance. Among these factors, freeze-thaw action in the plateau region is significantly controlled by spatiotemporal climate variations, with significant regional differences in freezing temperature, freeze-thaw amplitude, and freeze-thaw frequency. Furthermore, freeze-thaw cycles drive the continuous evolution of pore structure and microcracks, leading to a gradual, layered deterioration process from the surface inwards, promoting the entry of moisture and corrosive media, causing physicochemical damage, shortening lifespan, and increasing maintenance and safety risks. The long-term durability and service safety of concrete structures have become critical. Simply increasing the strength of the concrete structure or optimizing the mix proportions is insufficient to systematically address these problems. Therefore, there is an urgent need to develop concrete surface protection technologies suitable for the plateau environment to improve durability.

[0003] In existing technologies, patent CN113354325A uses a core-shell structure of "oil-phase hydrophobic core + water-phase dispersion shell" combined with conventional emulsification and dispersion processes to prepare a composite hydrophobic agent; patent CN118496510A uses "polycarboxylic acid macromolecules as the matrix, and hydrophobic segments are grafted by crosslinking agents" to regulate the molecular crosslinking density and enhance the anchoring and adsorption effect of the hydrophobic agent on the capillary walls of concrete; patent CN118344537A uses functional monomer polymerization to construct a three-dimensional network structure polycarboxylic acid hydrophobic agent, which balances coating density and hydrophobic stability through the dual effects of spatial network site blocking and surface hydrophobic film formation. All of the above solutions have the advantages of strong raw material versatility, good process operability, and suitability for conventional concrete engineering construction, and can specifically alleviate the problems of poor dispersion, short-lived hydrophobic effect, and weak interfacial bonding of traditional hydrophobic agents. However, these solutions share common limitations: they completely lack specific adaptation designs for the extreme environments of the Qinghai-Tibet Plateau, including strong ultraviolet radiation (above 1.3 W / m²), large temperature differences (daily temperature difference of around 30°C), frequent freeze-thaw cycles (more than 150 times per year), and low-pressure, windy conditions. They only focus on basic hydrophobic properties under normal conditions without optimizing components and structures for the special working conditions of the plateau. The raw materials used are all common general-purpose hydrophobic substrates and additives, without screening for aging-resistant, freeze-thaw-resistant, and low-pressure-stable raw materials suitable for the plateau environment. There are no specific functional designs for resistance to strong ultraviolet radiation, resistance to severe temperature differences, and resistance to repeated freeze-thaw cycles. Long-term service at high altitudes can easily lead to molecular degradation, deactivation of hydrophobic groups, and rapid performance decline. Some solutions rely on conventional polycarboxylic acid and ordinary silane compounding, without optimizing the penetration and bonding strength between the coating and porous concrete at high altitudes. Under low temperature and freeze-thaw cycles, interface debonding and hydrophobic channel breakage are likely to occur. The construction and curing conditions are all based on conventional room temperature standards, without considering the actual pain points of simple construction conditions, slow low temperature hydration, and rapid drying shrinkage in remote high-altitude areas. It is impossible to achieve rapid construction and long-term curing at room temperature, and it is difficult to meet the requirements of high weather resistance, high stability, and high adaptability for long-term protection of concrete structures on the Qinghai-Tibet Plateau.

[0004] In recent years, although some progress has been made in the research of superhydrophobic coatings, there are still some core technical pain points: First, high-performance hydrophobic raw materials such as fluorosilanes are expensive and their environmental friendliness is questionable; second, coating design focuses on the hydrophobic performance itself and ignores the interfacial stability and weather resistance in extreme environments; third, there is a lack of differentiated preparation schemes adapted to different environments, making it difficult to meet the construction and service requirements of plains at normal temperature and plateaus at extreme environments at the same time.

[0005] Therefore, developing a highly weather-resistant bissilane synergistic modified nano-calcium carbonate concrete hydrophobic coating and its preparation method is of great engineering significance and practical value for improving the long-term durability of concrete structures in extreme environments such as plateaus. Summary of the Invention

[0006] To address the shortcomings of existing hydrophobic coatings, such as poor weather resistance, unstable interfacial bonding, and insufficient adaptability of preparation processes in the extreme environment of high-altitude areas, this invention provides a dual-silane synergistic modified nano-calcium carbonate superhydrophobic coating, a concentrated solution, and its preparation method. Specifically designed for the multi-field coupled extreme environment of the Qinghai-Tibet Plateau, characterized by strong ultraviolet radiation, frequent freeze-thaw cycles, and wind and sand erosion, this invention offers a superhydrophobic coating that combines high weather resistance with long-term durability. Based on molecular structure design, this coating aims to construct a stable and permanent hydrophobic barrier within the concrete matrix through the selection and modification of key active components. While achieving cost control and environmental friendliness, the coating integrates superhydrophobicity, strong interfacial bonding, and extreme environmental tolerance, ultimately serving the construction of high-altitude infrastructure and significantly improving the freeze-thaw resistance and long-term service safety of engineering projects from a material perspective.

[0007] In a first aspect, a concentrated solution of a silane-synergistically modified nano-calcium carbonate superhydrophobic coating is provided, comprising: dodecyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, nano-calcium carbonate, nano-zinc oxide, formic acid, deionized water, and isopropanol.

[0008] In some embodiments, the concentrated solution of the bissilane synergistic modified nano-calcium carbonate superhydrophobic coating comprises, by mass percentage: 2%~10% dodecyltrimethoxysilane (DTMS) (preferably any two values ​​from the range of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%), 1%~8% 3-(isobutenoyloxy)propyltrimethoxysilane (KH-570) (preferably any two values ​​from the range of 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%), 5%~7% nano-calcium carbonate, 0.5%~2% nano-zinc oxide, 0.5%~2% formic acid, 10%~12% deionized water, and the balance being isopropanol.

[0009] In some embodiments, the concentrated solution of the bissilane synergistic modified nano-calcium carbonate superhydrophobic coating comprises, by mass percentage: 4%~5% dodecyltrimethoxysilane (DTMS), 2%~3% 3-(isobutenoyloxy)propyltrimethoxysilane (KH-570), 5%~6% nano-calcium carbonate, 1%~2% nano-zinc oxide, 0.5%~1% formic acid, 10%~11% deionized water, and the balance being isopropanol.

[0010] In some embodiments, the nano-calcium carbonate has a particle size ≤100nm, a surface rich in hydroxyl groups, and can undergo a condensation reaction with silanol molecules, serving as a micron-scale framework for a micro-nano dual roughness structure in the coating.

[0011] In some embodiments, the nano-ZnO particles have a diameter of 500 nm, are rich in hydroxyl groups on their surface, and also have UV shielding function. They can fill the gaps between nano-calcium carbonate particles to form a nanoscale secondary rough structure. Nano-calcium carbonate and nano-ZnO synergistically construct a stable micro-nano dual rough structure in the coating, significantly improving the coating's superhydrophobic properties and UV aging resistance, resulting in a contact angle ≥150°, a roll-off angle ≤10°, and a contact angle ≥150° after 1000h aging.

[0012] Secondly, a method for preparing a concentrated solution of a silane-synergistically modified nano-calcium carbonate superhydrophobic coating is provided, comprising: S1. After stirring isopropanol, deionized water and formic acid evenly, add DTMS and KH-570, stir evenly and let stand for hydrolysis to obtain a mixed silanol solution. S2. Add the mixed silanol solution obtained in step S1 to a mixture of nano-calcium carbonate and nano-ZnO, and sonicate to achieve a condensation reaction to obtain a mixed system. S3. The system after ultrasonic treatment in step S2 is heated and continuously stirred for reaction. After the system is cooled, it is filtered to obtain a superhydrophobic coating concentrate.

[0013] In some embodiments, in S1, isopropanol, deionized water, and formic acid are stirred at 10-40°C and 200-300 r / min for 10-15 min using magnetic or mechanical stirring to ensure uniform mixing of all components. Preferably, the temperature is any one of the ranges of 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or any two of the above values; the stirring speed is any one of the ranges of 200 r / min, 250 r / min, 300 r / min, or any two of the above values; and the stirring time is any one of the ranges of 10 min, 12 min, 13 min, 14 min, 15 min, or any two of the above values.

[0014] In some embodiments, the stirring time for adding DTMS and KH-570 in S1 is 5 min, and the standing time is 20-40 min, so that the two silanes are fully hydrolyzed to generate a mixed silanol solution containing long-chain alkyl groups and active double bonds. Preferably, the time is 20 min, 30 min, 40 min, or any two of the above values.

[0015] In some embodiments, the ultrasonic treatment temperature in S2 is controlled at 0~5℃, and the ultrasonic dispersion process is accompanied by low-speed stirring at a speed of 50~100r / min to prevent local agglomeration of nanoparticles.

[0016] In some embodiments, the ultrasonic treatment in S2 refers to using a probe-type ultrasonic cleaner with a frequency of 20kHz to ultrasonically disperse the nanoparticles for 20 to 40 minutes, preferably 20 minutes, 30 minutes, or 40 minutes, to achieve uniform dispersion of the nanoparticles and to cause in-situ condensation grafting of silanol molecules with the hydroxyl groups on the surface of the nanoparticles.

[0017] In some embodiments, the stirring speed in S3 is 140~285 r / min, and the stirring time is 1~5 h; preferably, the stirring speed is any one of the ranges of 140 r / min, 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, 220 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, or any two of the above values; preferably, the stirring time is any one of the ranges of 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, or any two of the above values. In some embodiments, the stirring device in S3 is a magnetically heated stirrer.

[0018] In some embodiments, the heating temperature rise rate in S3 is 5~8℃ / min to avoid uneven silanol condensation reaction and local self-polymerization caused by excessively rapid heating.

[0019] In some embodiments, the heating temperature in S3 is 60~70°C to promote the deep condensation of silanol molecules to form a three-dimensional cross-linked Si-O-Si network; preferably, the temperature is any one of 60°C, 65°C, 70°C, or any two of the above values.

[0020] Thirdly, a method for preparing a silane-synergistically modified nano-calcium carbonate superhydrophobic coating is provided, comprising: Step 1, Substrate Pretreatment: After standard curing of the concrete specimens, dry them and remove dust and impurities to ensure that the substrate is clean and dry; Step 2, spraying and coating: The superhydrophobic coating concentrate of the present invention is uniformly sprayed onto the surface of the pretreated concrete specimen to be protected; Step 3, Curing and Shaping: After spraying, the coating is cured and solidified in the environment to obtain a superhydrophobic coating.

[0021] In some embodiments, after standard curing of C40 and above strength grade concrete specimens for 28 days, they are dried in an oven at 60±5℃ for 48~52 h, cooled to room temperature, and surface dust is removed using oil-free compressed air to ensure that the substrate is clean and dry.

[0022] In some embodiments, a pneumatic spray gun is used to uniformly spray the prepared hydrophobic coating concentrate onto the surface of the pretreated concrete specimen to be protected.

[0023] In some embodiments, during the spraying process, if there are minor cracks (width ≤ 0.2 mm) on the concrete surface, the cracked areas should be sprayed first to ensure that the coating fully penetrates the cracks before the overall coating is applied.

[0024] In some embodiments, the spraying method is as follows: the distance between the spray gun nozzle and the concrete specimen surface to be protected is controlled at 20-30 cm, the spraying pressure is maintained at 0.3-0.5 MPa, and the spraying amount is strictly controlled at 30-35 g / cm³. 2 .

[0025] In some embodiments, the number of spraying applications is at least 2. Preferably, after the first spraying, the substrate is left to stand for 10 to 15 minutes until the coating has initially wetted the substrate before the second spraying is applied to avoid the coating from flowing or accumulating.

[0026] In some embodiments, the sprayed concrete specimens are cured in an environment with room temperature (20±5℃) and relative humidity ≤60% for 24~36 h.

[0027] Fourthly, a dual-silane synergistic modified nano-calcium carbonate superhydrophobic coating is provided, which is prepared by the preparation method described in this invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects: To address the challenges of concrete degradation in extreme environments like the Qinghai-Tibet Plateau, where strong ultraviolet radiation, frequent freeze-thaw cycles, and wind erosion can lead to moisture intrusion and structural deterioration, traditional concrete is susceptible to this problem. Furthermore, traditional hydrophobic coatings suffer from insufficient weather resistance, weak interfacial bonding, and difficulty adapting to extreme conditions. This invention discloses a highly weather-resistant, dual-silane synergistic modified nano-CaCO3 concrete hydrophobic coating, its concentrate, and its preparation method. Existing research often focuses on single hydrophobic properties or single-factor durability improvements, lacking specific adaptation designs for the multi-field coupled environment of high-altitude regions. Long-term service can lead to performance degradation, and there are also issues such as high raw material costs and insufficient environmental friendliness. Figure 1 and Figure 2As shown, this invention employs a differentiated preparation process—"mixed silanol preparation - in-situ grafting modification - siloxane network curing"—through precise formula design, coupled with a dedicated spraying and curing process. It utilizes DTMS and KH-570 dual silanes for synergistic crosslinking, combined with nano-CaCO3 and nano-ZnO to construct a micro-nano dual roughened structure. This simultaneously achieves superhydrophobic film formation on concrete surfaces and hydrophobic modification of shallow pore walls, exhibiting both low surface energy hydrophobic properties and high interfacial bonding stability. The core enhancement of this invention lies in the coating's weather resistance. It maintains stable superhydrophobicity even after temperature changes, UV aging, abrasion, peeling, and freeze-thaw cycles, with significantly reduced water absorption. It also exhibits high performance retention in alkaline environments, demonstrating outstanding water resistance and durability. This coating can be used independently as a superhydrophobic protective structure or as the bottom hydrophobic substrate in a multi-layered composite protective system, adapting to diverse engineering protection needs. Specifically: (1) Strong synergy of formulation and excellent comprehensive performance: Through the synergistic modification of nanoparticles by dual silane and precise proportion of components, the prepared coating has superhydrophobicity (contact angle ≥162.3°), strong adhesion (level 1), high weather resistance and freeze-thaw resistance. The water absorption rate of C40 concrete is reduced by 57.2%, and the mass loss rate after 200 freeze-thaw cycles is only 3.58%, which solves the problem of the single outstanding performance and the imbalance of comprehensive performance of traditional coatings.

[0029] (2) Excellent hydrophobic properties and outstanding comprehensive protection effect: Through the synergistic modification of nanoparticles by dual silane and precise component ratio, the coating has superhydrophobicity, strong adhesion, high weather resistance and freeze-thaw resistance. It can significantly reduce the water absorption rate of concrete and greatly improve the freeze-thaw resistance, anti-aging and wear resistance, effectively solving the problem of single hydrophobicity and insufficient comprehensive performance of traditional coatings.

[0030] (3) The superhydrophobic coating prepared by this invention has outstanding anti-aging properties and can be precisely adapted to the extreme service environment of strong ultraviolet radiation and alternating temperature and humidity on the Qinghai-Tibet Plateau. After aging, the structural integrity and interfacial bonding are excellent. The anti-aging mechanism is adapted to the stress coupling scenario of multiple environments on the plateau: through the synergistic design of dual silanes, the coupling effect of KH-570 not only enhances the internal cross-linking degree of the coating, but also strengthens the chemical bonding with the concrete substrate, effectively inhibiting the degradation of polymer chains caused by strong ultraviolet radiation; at the same time, the ultraviolet shielding function of nano ZnO and the structural support function of nano CaCO3 work together to avoid the failure of micro-nano rough structures under irradiation-temperature and humidity alternation. From the mechanism, it solves the pain point of insufficient anti-aging performance of traditional single silane coatings and difficulty in adapting to the complex environment of the plateau, providing long-term anti-aging protection for concrete structures.

[0031] (4) The superhydrophobic coating prepared by this invention has excellent antifreeze properties and can accurately resist the damage to concrete caused by frequent freeze-thaw cycles on the Qinghai-Tibet Plateau. This is reflected in the following: the mass loss rate under high and low temperature freeze-thaw cycles is significantly reduced, the structural integrity and coating stability are outstanding after long-term freeze-thaw cycles, and the antifreeze mechanism is adapted to the core pain points of freeze-thaw cycles on the plateau: through the dual silane synergistic design, on the one hand, the constructed superhydrophobic protective layer can effectively inhibit capillary water absorption and reduce water intrusion into the concrete, thereby reducing the crystallization pressure and microstructure damage caused by "water freezing expansion (volume expansion of about 9%)" from the root; on the other hand, KH-570 enhances the interfacial adhesion between the coating and the concrete substrate, avoiding the stress caused by freeze-thaw cycles that leads to coating peeling failure, solving the problem that ordinary hydrophobic coatings have limited antifreeze effects due to insufficient interfacial adhesion and hydrophobic stability, providing long-term antifreeze protection for concrete structures in the frequent freeze-thaw environment of the plateau, and significantly improving their service durability. The superhydrophobic coating prepared by this invention exhibits strong interfacial bonding and outstanding durability. The synergistic effect of pretreated nano-calcium carbonate and KH550 enables the coating to form multiple chemical bonds with the concrete substrate, resisting the erosion of temperature stress and freeze-thaw cycles. Performance degradation after temperature cycling is minimal, effectively extending the service life of concrete structures. After coating application, the average water absorption rate of concrete decreases by ≥57.2%, and the mass loss rate after 200 freeze-thaw cycles is ≤3.58%.

[0032] (5) The preparation process and construction process are significantly different and do not belong to the homogeneous conventional process. The present invention adopts a segmented temperature-controlled reaction process, and the process route is different from the traditional superhydrophobic coating, with significant differentiation characteristics. The whole process only uses common unit operations such as basic stirring, ultrasonication, and heating, which are standard in the industry. However, the overall process route, process combination, parameter design, layered reaction logic, and construction adaptability are significantly different, which has process innovation and wide environmental adaptability: the conventional process meets the construction needs of plain normal temperature environment, and the special process is optimized for plateau extreme environment. Through raw material pretreatment, reaction rate control, post-treatment enhancement and other links, the stability of the coating under strong ultraviolet and large temperature difference is improved, and precise protection is achieved in different environments.

[0033] Terminology Explanation Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0034] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0035] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0036] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0037] In the following content, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. The value of each figure may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%, etc. Whenever a figure with a value of N is disclosed, any figure with a value of N±1%, N±2%, N±3%, N±5%, N±7%, N±8%, N±10%, N±15%, or N±20% will be explicitly disclosed, where "±" indicates addition or subtraction.

[0038] The mass percentage of each component is based on a total mass of 100%, with isopropanol as the solvent balance used to adjust the system to 100%. Attached Figure Description

[0039] Figure 1 The preparation process and spraying test diagram of the silane synergistic modified nano-calcium carbonate coating are shown.

[0040] Figure 2This diagram illustrates the mechanism of silane-mediated modification of nano-calcium carbonate coatings. In the diagram, DTMS and KH570 hydrolyze under acid catalysis to generate silanols (Si-OH), which subsequently undergo condensation with hydroxyl groups on the nanoparticle surface to form Si-OM bonds. Simultaneously, the silanols further condense to form a three-dimensional Si-O-Si network. After spraying, a permeable hydrophobic layer, modified nanoparticles, and a Si-O-Si network are formed on the substrate surface.

[0041] Figure 3 The test results are shown in the figure to investigate the effect of different DTMS contents on the hydrophobic properties of the superhydrophobic coating.

[0042] Figure 4 The test results are shown in the figure to investigate the effect of different KH570 contents on the hydrophobic properties of the superhydrophobic coating.

[0043] Figure 5 The figure shows the effect of temperature cycling test on hydrophobic properties.

[0044] Figure 6 The figure shows the effect of strong ultraviolet irradiation on hydrophobic properties.

[0045] Figure 7 SEM images of the concrete surface with the superhydrophobic coating applied at 5kx magnification. (a) Substrate surface before aging, (b) Substrate surface after aging.

[0046] Figure 8 This is a graph showing the relationship between the number of freeze-thaw cycles and the mass loss rate.

[0047] Figure 9 The images show the changes in appearance of the specimens after freeze-thaw cycles. (a) Control group (0 freeze-thaw cycles); (b) Control group (200 freeze-thaw cycles); (c) Spray-coated group (0 freeze-thaw cycles); (d) Spray-coated group (200 freeze-thaw cycles). It can be seen that the spray-coated group showed no peeling or cracking after 200 freeze-thaw cycles, and its structural integrity was good.

[0048] Figure 10 This diagram illustrates the effect of peeling on the hydrophobic properties of the coating described in this invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0050] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0051] Table 1 Raw materials for hydrophobic coating configuration

[0052] In this invention, room temperature / normal temperature refers to 20~30℃, preferably 25~30℃. The temperature of the ice water bath is 0~5℃, preferably 3~5℃.

[0053] All mass percentages in this specification are approximate values ​​relative to the total mass of the concentrate. If the sum of the components is less than or more than 100%, the difference is made up or subtracted by adding the solvent isopropanol to keep the total mass percentage of the system constant at 100%.

[0054] Preparation Example 1 The concentrated solution of bissilane synergistic modified nano-CaCO3 superhydrophobic coating, by mass percentage, comprises: Raw materials: DTMS: 4.0%, KH570: 2.0%, nano calcium carbonate: 5.0%, nano zinc oxide: 1.0%; Solvent: Deionized water: 10.0%; Catalyst: 85wt% formic acid; 0.5% Isopropanol: Bring the balance to 100%.

[0055] The preparation method of the concentrated solution of nano-CaCO3 superhydrophobic coating with synergistic modification by bissilane includes the following steps: S1 Preparation of mixed silanol solution: Add isopropanol, deionized water and formic acid to a container, stir at 300 r / min at room temperature for 10-15 min until the system is homogeneous, add DTMS and KH-570, continue stirring for 5 min, then cover with a watch glass and let stand at room temperature for 30 min to allow the two silanes to fully hydrolyze, generating a mixed silanol solution containing long-chain alkyl groups and active double bonds, for later use; S2 In-situ chemical grafting modification: Isopropanol was added to a container, and nano-CaCO3 and nano-ZnO were added with stirring at 300 r / min at room temperature. The system was placed in an ice-water bath and treated with a probe-type ultrasonic cleaner at a frequency of 20 kHz for 10 min. The mixed silanol solution obtained in step S1 was added to it and treated with a probe-type ultrasonic cleaner at a frequency of 20 kHz for 30 min at a speed of 50 r / min to achieve component dispersion and condensation reaction between silanol molecules and hydroxyl groups on the surface of nanoparticles, thus completing the in-situ chemical grafting. S3 Siloxane Network Formation and Post-treatment: The system after ultrasonic treatment in step S2 was placed on a magnetically heated stirrer at a speed of 200 r / min and slowly heated to 70℃ at a rate of 5~8℃ / min and stirred continuously for 3h to promote the condensation of silanols to form a siloxane network and lock the modified nanoparticles; after the system cooled to room temperature, it was filtered to obtain a milky white hydrophobic coating concentrate.

[0056] Preparation Example 2 The concentrated solution of bissilane synergistic modified nano-CaCO3 superhydrophobic coating, by mass percentage, comprises: Raw materials: DTMS: 5.0%, KH570: 2.5%, nano calcium carbonate: 6.0%, nano zinc oxide: 2.0%; Solvent: Deionized water: 11.0%; Catalyst: 85wt% formic acid: 1%; Isopropanol: Bring the balance to 100%.

[0057] The preparation process is the same as in Example 1.

[0058] Preparation Example 3 The concentrated solution of bissilane synergistic modified nano-CaCO3 superhydrophobic coating, by mass percentage, comprises: Raw materials: DTMS: 4.6%, KH570: 2.3%, nano calcium carbonate: 5.5%, nano zinc oxide: 1.5%; Solvent: Deionized water: 10.5%; Catalyst: 85wt% formic acid; 0.8% Isopropanol: Bring the balance to 100%.

[0059] The preparation process is the same as in Example 1.

[0060] Preparation Example 4 The concentrated solution of bissilane synergistic modified nano-CaCO3 superhydrophobic coating, by mass percentage, comprises: Raw materials: DTMS: 3.0%, KH570: 1.5%, nano calcium carbonate: 7.0%, nano zinc oxide: 0.5%; Solvent: Deionized water: 12.0%; Catalyst: 85wt% formic acid; 1.5% formic acid; Isopropanol: Bring the balance to 100%.

[0061] The preparation process is the same as in Example 1.

[0062] Preparation Example 5 The difference from Example 1 is that the DTMS content is changed, while the contents of other components remain unchanged, with the balance being isopropanol. The preparation process is the same as in Example 1. Table 2 shows the changes in DTMS content.

[0063] Table 2

[0064] Preparation Example 6 The difference from Example 1 is that the KH570 content is changed, while the contents of the other components remain unchanged, with the remainder being isopropanol. The preparation process is the same as in Example 1. Table 3 shows the changes in KH570 content.

[0065] Table 3

[0066] Preparation Example 7 The difference from Example 1 is that nano-calcium carbonate and nano-zinc oxide are missing, while the remaining components and preparation process are the same as in Example 1.

[0067] Application Example 1 The protective coating application process includes the following steps: ①. Substrate pretreatment: After the C40 grade concrete specimens are cured for 28 days according to standard, they are placed in an oven at 60±5℃ for 48 hours to dry. After cooling to room temperature, oil-free compressed air is used to blow evenly along the concrete surface to remove floating dust, loose particles and other attachments, ensuring that the substrate is clean, dry and free of loose impurities. ②. Spraying Application: The hydrophobic coating concentrate prepared according to this invention is uniformly sprayed onto the pretreated concrete surface to be protected using a pneumatic spray gun. The distance between the spray gun nozzle and the concrete surface is controlled at 20-30cm, and the spraying pressure is maintained at 0.3-0.5MPa. The spraying amount is strictly controlled at 30g / cm³. 2 Apply the coating in two coats. After the first coat, let it stand for 10 minutes to allow the coating to initially penetrate the substrate before applying the second coat. This prevents the coating from flowing or piling up. If there are fine cracks (width ≤ 0.2mm) on the concrete surface during spraying, focus on spraying the cracked areas first to ensure that the coating fully penetrates the cracks before applying the overall coating. ③. Curing and shaping: After spraying, place the concrete specimen in an environment of 20±5℃ and relative humidity ≤60% for 24 hours. During the curing period, avoid water and rain on the surface, and prevent it from being contaminated with dust, oil, or subjected to mechanical collisions and scratches. After the curing period, the coating will be cured and shaped.

[0068] Detection Example 1 Hydrophobic performance test: The concentrated hydrophobic coating solutions prepared in Examples 1, 5, 6, and 7 were used to prepare superhydrophobic coatings according to the method described in Example 1. The hydrophobic performance was tested according to the hydrophobic performance test standard, and the results are as follows: Figure 3 and Figure 4 As shown.

[0069] The hydrophobicity performance test standard is as follows: This test uses a concrete slab with dimensions of 100mm×100mm×20mm as the test substrate. The coating contact angle and roll-off angle tests are performed in accordance with GB / T 26490-2011 "Test Method for Superhydrophobic and Amphiophore Properties of Nanomaterials". The sample size meets the requirements of the standard.

[0070] like Figure 3 As shown, when DTMS is missing, the surface energy of the superhydrophobic coating increases significantly, and the water contact angle drops sharply from 157.1° to 110.6°, completely losing its superhydrophobic ability and only possessing basic hydrophobic effects, unable to inhibit capillary water absorption by concrete; as the content of DTMS increases, the hydrophobic performance also improves accordingly, with the roll-off angle first decreasing and then increasing. The hydrophobic coating prepared with the hydrophobic coating concentrate prepared in Example 1 has the best overall performance.

[0071] like Figure 4 As shown, when KH-570 is missing, the interfacial adhesion and structural stability of the superhydrophobic coating decrease sharply. Although it can still reach a contact angle of 141.3°, the roll-off angle increases significantly with the increase of KH570 content, while the anti-peeling / anti-wear performance is greatly reduced, and the hydrophobicity fails rapidly after temperature change and ultraviolet aging.

[0072] Example 7 did not add nano-CaCO3 and nano-ZnO, so the superhydrophobic coating could not construct a micro-nano dual rough structure. The water contact angle could only reach a maximum of 141.3°, which could not break through the 150° superhydrophobic threshold. The self-cleaning and anti-wetting abilities were significantly weakened.

[0073] In summary, only when DTMS provides low surface energy, KH-570 strengthens the interface and film formation, and nanoparticles construct a rough structure can the coating simultaneously achieve superhydrophobic properties with a contact angle ≥162.3° and a roll-off angle ≤9°, as well as comprehensive properties such as strong weather resistance, high adhesion, and freeze-thaw resistance. This fully demonstrates that the system is not a simple superposition of components, but a synergistic optimization system with complementary functions of multiple components.

[0074] Detection Example 2 Water absorption performance test: The hydrophobic coating concentrates prepared in Examples 1, 5, 6 and 7 were used to prepare superhydrophobic coatings in the manner of application in Example 1. The water absorption performance test was conducted according to the water absorption performance test standard. The results are shown in Table 4.

[0075] The standard for water absorption performance testing is as follows: The conventional national standard GB / T 50081-2019 uses high-temperature drying at (105±5)℃, which easily causes thermal aging and performance failure of organic hydrophobic coatings. Therefore, this test method is appropriately adjusted based on the GB / T 50081-2019 standard to evaluate the influence of hydrophobic coatings on the water absorption performance of concrete. A 100mm×100mm×100mm cubic concrete specimen is used. After curing for 3 days, a hydrophobic coating is sprayed on. Three specimens are taken for each working condition to measure their water absorption rate. The arithmetic mean of the water absorption rates of the three specimens is then calculated as the final water absorption rate. The specimen is placed in an oven at (80±5)℃ for 24 hours, then removed and weighed (m0). After removal, water is injected so that the surface of the specimen is immersed in water to a height of not less than 20mm. After soaking in water for 24 hours, the concrete surface is wiped with a wrung-out damp cloth. After drying the surface, the specimen is weighed (m1). The formula for calculating the water absorption rate of the specimen is shown in equation (1). After spraying a hydrophobic coating onto a 100mm×100mm×20mm specimen as a substrate, the test was conducted. The substrate was removed and allowed to dry naturally each day before the hydrophobicity test was performed. The test was conducted for a total of 5 days.

[0076] Equation (1) Where: W—water absorption rate of the specimen (%); m0—mass of the specimen after drying (g); m1—mass of the specimen after water absorption (g).

[0077] Table 4 Water Absorption Rate of Hydrophobic Coating

[0078] Note: C-0 is the control group concrete, and the rest are sprayed hydrophobic coating concrete. The substrate is tested using 100mm×100mm×100mm specimens.

[0079] Table 4 shows that the average water absorption rate of the untreated control group concrete (C-0) was 5.44%. However, the average water absorption rate of the specimens after spraying the composite coating (especially C-1) was significantly reduced to 2.29%, with the coating reducing the concrete's water absorption rate by approximately 57%. This significant reduction in water absorption rate is directly attributed to the hydrophobic-hydrophilic dual barrier formed by the coating on the concrete surface and within the shallow pores. The silane component penetrates the pores through capillary action and reacts with the hydroxyl groups in the concrete to form a hydrophobic silica network, fundamentally altering the properties of the pore surface and making it difficult for water molecules to wet and penetrate. For regions like the Qinghai-Tibet Plateau, water absorption rate is crucial as it significantly reduces water intrusion, effectively preventing freeze-thaw damage. Furthermore, lower water absorption rate means preventing aqueous solutions from entering the concrete interior, protecting the reinforcing steel from corrosion.

[0080] The water absorption rates from tests C-4, C-5, and C-6 show that the multi-component synergistic effect is significant. The absence of any core component prevents the achievement of optimal performance. The coating prepared in this embodiment forms a strong synergistic system through the precise ratio of DTMS main hydrophobic component, KH-570 coupling reinforcement component, and nano CaCO3 / ZnO micro / nano framework.

[0081] Detection Example 3 Temperature cycling tests are used to evaluate the structural stability and functional retention of coatings under alternating hot and cold conditions, reflecting the degree of fatigue damage to materials under repeated thermal expansion and contraction coupled with water absorption and dehydration. Based on this, this application simulates the large temperature difference environment of a high-altitude region through controlled high and low temperature cycling, tracking changes in contact angle and roll-off angle to verify the stability and long-term application feasibility of the dual-silane synergistic modified nano-CaCO3 coating under temperature stress. The results are as follows: Figure 5 As shown.

[0082] The temperature change resistance test standard is as follows: To verify the application of the dual-silane synergistic modified nano-CaCO3 coating in a high-altitude environment with large temperature differences, this application conducts high and low temperature cycling tests, which can effectively simulate the coating's performance under temperature changes and verify whether the coating has temperature change cycling resistance and long-term stability. The temperature change cycling is conducted according to JG / T 25-2017 "Test Method for Temperature Change Resistance of Architectural Coatings": The prepared and cured coating test panels are first immersed in a room temperature water bath for 18 hours, then removed, placed on their sides, and then placed... The sample was frozen in a low-temperature chamber at 20±2℃ for 3 hours, and then immediately transferred to a constant-temperature chamber at 50±2℃ for 3 hours. This constituted one temperature change cycle. The cycle was repeated 5 times, and the contact angle and roll-off angle were measured on the surface of the sample after each cycle. This was to comprehensively determine the impact of the temperature change cycle on the hydrophobic function and structural stability of the coating.

[0083] like Figure 5 As shown, after five high and low temperature cycles, the initial contact angle of the test sample decreased by only 2.2°, and the roll-off angle increased by only 7.1%, maintaining a superhydrophobic state throughout (contact angle ≥150°), with minimal degradation in hydrophobic properties. The coating of this invention effectively resists alternating thermal stress caused by thermal expansion and contraction, maintaining stable interfacial adhesion and structural integrity during temperature cycling, avoiding functional degradation and structural damage, and exhibiting excellent temperature resistance, making it suitable for concrete protection requirements in extreme high-altitude environments.

[0084] Detection Example 4 The hydrophobic coating concentrate prepared in Example 1 was used to prepare superhydrophobic coatings in accordance with the method described in Example 1, simulating a high-altitude strong ultraviolet environment (radiation intensity 1.3 W / m²). 2 It is 0.68 W / m higher than the plain standard. 2Accelerated aging tests (8h irradiation + 10min rain + 4h dew cycle, totaling 120h) were conducted to test hydrophobic properties, and the results are as follows: Figure 6 and Figure 7 As shown.

[0085] Anti-aging performance testing standards: Anti-aging performance is usually evaluated according to the test methods in the standard "Artificial Climate Aging and Artificial Radiation Exposure to Filtered Xenon Arc Radiation for Paints and Varnishes" (GB / T 1865-2009). This test uses a standard plain radiation intensity of typically 0.68 W / m². 2 As altitude increases, radiation intensity also increases. To simulate a high-altitude environment, this study increased the radiation intensity of the benchtop anti-aging test chamber to 1.3 W / m². 2 The aging program was set to: 8h (50℃, 1.3W / m²). 2 Irradiation + 10 min rain + 4 h (10℃) dew, and after continuous operation for 1000 h, the changes in hydrophobic properties of the samples under each working condition were measured.

[0086] like Figure 6 As shown, during the accelerated aging process of 1000 hours, the hydrophobic angle of the coating slowly decreased from the initial 161.7° to 151.2° after 1000 hours, maintaining a superhydrophobic state above 150° throughout the process; simultaneously, the roll-off angle slightly increased from 9.61° to 10.56°. Both changes were small and exhibited a near-linear, gradual decline, without any abrupt performance changes or precipitous drops. This indicates that under the combined stress of ultraviolet radiation, temperature and humidity cycling, the low-energy chemical composition and micro / nano rough structure of the coating surface maintained good stability and did not undergo large-scale damage. The slight decrease in the hydrophobic angle and the simultaneous slight increase in the roll-off angle typically indicate a subtle but systematic change in the coating surface state. Under aging stress, the outermost silane molecular chains degrade or undergo conformational changes, leading to a slight increase in surface energy. The interface between nanoparticles and the matrix, or the particles themselves, suffers microscopic damage, resulting in a slight decrease in the uniformity of the surface rough structure, thus slightly increasing the pinning effect of water droplets. Nevertheless, the small magnitude of the change precisely demonstrates the system's excellent synergistic anti-aging capabilities. The obtained data provides crucial evidence for assessing the feasibility of this coating's application in high-altitude regions.

[0087] like Figure 7 As shown, when not aged ( Figure 7 (a)) Numerous fine particle aggregates are visible on the surface, forming a continuous rough layer. This micro-nano stacking originates from the locking and film formation of modified nano-CaCO3 by a silicon-oxygen network formed by the hydrolysis-condensation of bissilanes. Locally, unhydrated particles are still visible embedded within the particle layer; after aging ( Figure 7(b) The morphology tends to be non-uniform and accompanied by the manifestation of pores and defects. The mechanism can be attributed to the photo-oxidation and chain breakage effect of strong ultraviolet light and temperature alternation on organosilicon chain segments, which causes the film layer to gradually pulverize and become brittle and reduce the interparticle locking continuity. At the same time, rain cycles cause the dynamic rearrangement of silane bond structure through hydrolysis and re-condensation. Combined with the interfacial fatigue caused by alternating hot and cold temperatures, the particle matrix bonding weakens and the edges of the aggregates peel off first, thus forming local cavities, structural collapse and regions of non-uniform composition and structure.

[0088] The system maintains a high contact angle even after UV exposure, indicating that the hydrophobic mechanism relying solely on organic segments has been transformed into a synergistic mode of organic low surface energy + inorganic particulate framework + silicon-oxygen network consolidation. Nano-ZnO provides some UV shielding, KH-570 enhances the bonding between the particulate layer and the substrate, and the low surface energy layer provided by DTMS is not easily lost due to the network structure constraint. Therefore, the system exhibits good overall resistance to UV degradation.

[0089] Detection Example 5 Hydrophobicity test after freeze-thaw cycles: The freeze-thaw resistance test was conducted according to the "Standard for Test Scheme of Long-Term Performance and Durability of Concrete" (GB / T 50082-2024). Three 100mm×100mm×100mm concrete specimens were used for each test condition. The freeze-thaw cycle procedure was performed according to section 4.2 of (GB / T 50082-2024). After every 25 cycles, the specimens were removed, surface debris was cleaned, and the surface was dried. External damage was checked, and the mass loss rate of the specimens was measured. If the quality loss rate exceeds 5%, stop the test immediately. The results are as follows: Figure 8 and Figure 9 As shown.

[0090] The formula for the mass loss rate is as shown in equation (2): Equation (2) —The mass loss rate of the i-th concrete specimen after n freeze-thaw cycles, accurate to 0.01%. W0i—The mass (g) of the i-th concrete specimen before the freeze-thaw cycle test; Wni—The mass (g) of the i-th concrete specimen after n freeze-thaw cycles.

[0091] Water absorption rate can only indirectly reflect the freeze-thaw resistance of concrete with this composite coating. In this study, the rapid freezing method of the freeze-thaw cycle test was used as a reference. The mass of the concrete specimens with the sprayed superhydrophobic coating was measured and compared with the control group every 25 freeze-thaw cycles until the specimens were destroyed.

[0092] like Figure 8As shown, the mass loss rate of the coating test sample of the present invention was only 3.58%, and in the early stage, due to the coating's ability to prevent water penetration and avoid frost heave and peeling, a slight negative mass increase was also observed. In contrast, the mass loss rate of the blank control group after 200 freeze-thaw cycles reached 10.68%, and the mass loss rate of the ordinary hydrophobic coating control group (without KH-570 synergistic modification, Example 6-1) was 6.82%. The coating of the present invention has a much better anti-freeze protection effect on concrete than the control group and can significantly reduce material loss caused by freeze-thaw cycles.

[0093] like Figure 9 As shown, after 200 freeze-thaw cycles, the surface of the test sample with the coating of the present invention remained intact without peeling or cracking, with only very slight mortar powdering at the edges. The coating remained tightly bonded to the concrete substrate. In contrast, the blank control group showed large-area loosening and peeling, aggregate exposure, and obvious through cracks. The ordinary hydrophobic coating control group showed local coating peeling, fine cracks on the concrete surface, and flaking. The coating of the present invention can maintain its structural stability during repeated freeze-thaw cycles, while effectively protecting the concrete substrate from freeze-thaw damage.

[0094] Detection Example 6 The hydrophobic coating concentrate prepared in Example 1 was used to prepare superhydrophobic coatings according to the method described in Example 1. After 30 tape peels, the effect of peeling on the hydrophobic properties was tested, and the results are as follows: Figure 10 As shown.

[0095] like Figure 10 As shown, the contact angle of the coating is still ≥153.1° after 30 tape peels and 146.9° after 50 peels, indicating strong interfacial adhesion and the ability to resist mechanical disturbances in high-altitude environments.

[0096] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A concentrated solution of nano-calcium carbonate superhydrophobic coating with synergistic modification by dual silanes, characterized in that, include: Dodecyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, nano-calcium carbonate, nano-zinc oxide, formic acid, deionized water, and isopropanol.

2. The superhydrophobic coating concentrate according to claim 1, characterized in that, The concentrated solution of the silane-synergistic modified nano-calcium carbonate superhydrophobic coating comprises, by mass percentage: 2%~10% dodecyltrimethoxysilane, 1%~8% 3-(isobutenoyloxy)propyltrimethoxysilane, 5%~7% nano-calcium carbonate, 0.5%~2% nano-zinc oxide, 0.5%~2% formic acid, 10%~12% deionized water, and the balance being isopropanol.

3. The superhydrophobic coating concentrate according to claim 1, characterized in that, The particle size of the nano-calcium carbonate is ≤100nm; Alternatively, the nano-zinc oxide particles have a diameter of 500 nm; Alternatively, the mass ratio of dodecyltrimethoxysilane to 3-(isobutyryloxy)propyltrimethoxysilane is 1:

1.

4. A method for preparing the superhydrophobic coating concentrate according to any one of claims 1 to 3, characterized in that, include: S1. After stirring isopropanol, deionized water and formic acid evenly, add dodecyltrimethoxysilane and 3-(isobutenoyloxy)propyltrimethoxysilane, stir evenly and let stand for hydrolysis to obtain a mixed silanol solution. S2. Add the mixed silanol solution obtained in step S1 to the mixed solution of nano calcium carbonate and nano zinc oxide, and sonicate the reaction to obtain a mixed system. S3. The system after ultrasonic treatment in step S2 is heated and continuously stirred for reaction. After the system is cooled, it is filtered to obtain a superhydrophobic coating concentrate.

5. The preparation method according to claim 4, characterized in that, In S1, isopropanol, deionized water and formic acid are stirred at 10~40℃ and 200~300r / min for 10~15min, using magnetic stirring or mechanical stirring. Alternatively, add DTMS and KH-570 to S1 and stir for 5-10 minutes, then let it stand for 20-40 minutes.

6. The preparation method according to claim 4, characterized in that, In S2, the ultrasonic treatment temperature is controlled at 0~5℃, and the ultrasonic dispersion process is accompanied by low-speed stirring at a speed of 50~100r / min. Alternatively, in S2, ultrasonic treatment refers to ultrasonic dispersion for 20-40 minutes using a probe-type ultrasonic cleaner with a frequency of 20kHz. Alternatively, in S3, the stirring speed is 140~285 r / min, and the stirring time is 1~5 h; Alternatively, the stirring device in S3 is a magnetically heated stirrer; Alternatively, the heating rate in S3 is 5~8℃ / min; Alternatively, the heating temperature in S3 is 60~70℃.

7. A method for preparing a silane-synergistically modified nano-calcium carbonate superhydrophobic coating, characterized in that, include: Step 1, Substrate Pretreatment: After standard curing of the concrete specimens, dry them and remove dust and impurities to ensure that the substrate is clean and dry; Step 2, spraying: uniformly spray the superhydrophobic coating concentrate according to any one of claims 1 to 3 or the superhydrophobic coating concentrate prepared by the preparation method according to any one of claims 4 to 6 onto the surface of the pretreated concrete specimen to be protected. Step 3, Curing and Shaping: After spraying, the coating is cured and solidified in the environment to obtain a superhydrophobic coating.

8. The preparation method according to claim 7, characterized in that, The spraying method is as follows: the distance between the spray gun nozzle and the concrete specimen surface to be protected is controlled at 20~30cm, the spraying pressure is maintained at 0.3~0.5MPa, and the spraying amount is strictly controlled at 30~35g / cm³. 2 .

9. The preparation method according to claim 7, characterized in that, The sprayed concrete specimens were cured in an environment of 20±5℃ and relative humidity ≤60% for 24~36 h.

10. A dual-silane synergistic modified nano-calcium carbonate superhydrophobic coating, characterized in that, Prepared by the preparation method according to any one of claims 7 to 9.

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